Damping paper fob copying-presses



accompanyin UNITED STATES PATENT oEEioE.

GEO. BURNHAM, 0F PHILADELPHIA, PENNSYLVANIA.

DAKPING PAPER F03 COPYING-PRESSES.

Specification of Letters Patent No. 7,851, dated December 24, 1850.

To all whom. it muy concern.'

Be it known that I, Gronau BUuNiiAifof the city and county of Philadelphia and State of Pennsylvania, have invented a new and useful Improvement in the Mode of Dampening Paper for Copying-Presses, of which the followin is a full, clear,"and exact description, re erence being had to the drawing, which forms p art of this speci cation and represents a view in 1perspective of my dampening tablet.

aper for copying letters by means of a coplyin press has heretofore been dampened eit er y drawing over it a brush inoistened with water, by laying upon it a cloth which has previously been dipped in water, or in some other analovous manner. These methods are all objectionable for the reason that it requires a very nice graduation ofthe water to dampen the paper to the requisite degree, and as the water is generally applied in excess it is necessary toinibibe the superfluous moisture by bibulius aper. These methods therefore are not on y'objectionable on account of the time required but are so also for the reason that it is extremely diliicultto dampen the paper to the pro er point, and hence it is diicult to pr uce good copies.

The object of my invention is to obviate these objections and it consists in a tablet of some suhstancefwhich is impermeable'to moisture and whose surface is roughened or burred up evenly throughout its wholeextent in sucli manner that the inequalities thereon will retain a suicient amount of moisture to dampen a sheet of paper to the r uisite degree. n order to repare such tablets I take a thin sheet o? metal (A) a little larger than the sheet which it is intended to dampen and form a crease in one of its edges (as at b) in order to stillen it, I then subject it to the action of a machine snmmeans ot which its surface is roughened in an equable manner. When the tablet thus made is to be used, it is lield by the left hand in the position represented, in the accom. panying drawing and a sponge previously dipped in water is passed by the right hand over its roughened surface. In this operation the inequalities in t-he surface of the tablet receive and retain a certain amount of water which as the plate is roughened in an equable 'manner is evenly distributed over its whole surface. The tablet thus moistened is laid upon the sheet to be dampened and pressure is applied to bring the two in contact with each other as the copying paper is bibulous it immediately absorbs the moisture from the tablet and is consequently dampened in an equable'manner throughout its whole extent. As the tablet is of itself impremeable to moisture no morewater can be applied to it in this manner than can be retained by the inequalities of its roughencd surface, hence, with ordinary care on the part of the operator, the quantity of moisture transferred to the paper is regulated almost as exactly as if it was weighed out at cach operation.

I do not oonne myself to the employment of sheet-metal is a material for my dampening'tabletsas many other impermeable materials are well suited to the purpose,

What I claim as m Y invention and desire to secure by Letters atent is A dampcning tablet constructed substantially as herein described of some impermeable material.

GEO. BURNHAM.

'itnesses:

W. R. SMiTH, GEORGE W. Hmri'. 

